CHAP. 2. 10. OF CLOUDS. 69 



SECTION X. 



Of certain Effects of the different Modifications 

 on each other, by Approximation., or with 

 Coalescence. 



It has been already stated, that the effect of 

 the. coalescence of two different modifications, 

 as, for example, of cumulus with cirrus, has 

 been the production of the cumulostratus, 

 and finally nimbus ; and also that nimbus has 

 appeared to result from the vicinity of two 

 different modifications, particularly when the 

 interfused air has been damp. I proceed now 

 to speak of more transitory effects produced 

 on clouds by the approximation of others of a 

 different modification. The most remarkable of 

 these is the conversion of cirrus or cirrostratus 

 into cirrocumulus, on the approach of cumulus, 

 or cumulostratus. On the 12th June, 1811, the 

 weather being showery, with clear intervals, 

 while looking out of window at Plaistow, in 

 company with M. Howard, I observed a cirrus 

 scattered about in the East. Cumuli were at 

 the same time flying along in a lower current of 

 air : presently a large cumulus passed apparently 



